Design for an Interface in Oxyhalide-Based All-Solid-State Lithium Metal Batteries

Oxyhalide solid-state electrolytes (SSEs) exhibit high ionic conductivity and good compatibility with high-voltage cathodes, presenting notable application prospects. However, the oxyhalide SSEs exhibit poor interface compatibility with lithium metal anodes, which limits their use in all-solid-state lithium metal batteries (ASSLMBs). In this study, we utilized the spontaneous reactions of SSEs with lithium metal to regulate the composition and structure of the solid electrolyte interface (SEI). By adjusting the composition of the SSEs, we promoted the in situ formation of a highly stable and kinetically favorable SEI. The in situ SEI demonstrated uniformity and compactness, while the synergistic effects of LiCl, LiF, and Y 2 O 3 enhanced interface stability. The lithium symmetric cells (Li|LTOC-YF 3 |Li) stably cycled for over 11,000 h (10.0 mA/cm 2, 10.0 mAh/cm 2 ) and achieved a high critical current density (CCD) of 12.7 mA/cm 2 at a capacity of 12.7 mAh/cm 2 . The Li|LTOC-YF 3 |NCM88 ASSLMB maintained over 150 cycles with 92% capacity retention at 25 °C. Meanwhile, it exhibits excellent electrochemical stability at 50 °C. Notably, the Li|LTOC-YF 3 |LCO ASSLMB at 0.1 C (2.5–4.6 V) displayed a high specific capacity of 108 mAh/g at −50 °C while maintaining a stable cycling performance. Overall, the use of the LTOC-YF 3 SSE in the ASSLMB demonstrates its remarkable electrochemical performance across a broad temperature range.